Opening multiple terminals gives resource busy errors

Description

run an additional terminal,
in the initial terminal you'll see:

could not open /dev/pt/p0: Device/File/Resource busy
could not open /dev/pt/p1: Device/File/Resource busy
could not open /dev/pt/p2: Device/File/Resource busy
.. {snip}
could not open /dev/pt/pf: Device/File/Resource busy
could not open /dev/pt/q0: Device/File/Resource busy